Process of forming twist-drills.



No. 758,041. PATBNTBD APR. 26, 1904.

. R. L. BARCLAY.

PROCESS OF FORMING TWIST DRILLS.

APPLICATION FILED P313, 28, 1903.

K0 MODEL.

' WITNESSES: N%T0/? BY I I W J 7 ATTORNEY Patented April 26, 1904.

PATENT OFFICE.

ROBERT L. BARCLAY,

OF NEW YORK, N. Y.

PROCESS OF FORMING TWIST-DRILLS.

SPECIFICATIONforming part of Letters Patent No. 758,041, dated April 26,1904. Application filed. February 28, 1903. Serial No. 145,593. (Nomodel.)

To all whom it may concern.-

Be it known that I, ROBERT L. BARCLAY, a citizen of the United States,residing in the borough of Brooklyn, in the county of Kings and city andState of New York, have invented an Improved Process ofFormingTwist-Drills, of which the following is a specification.

This invention relates to the manufacture of twistwlrills; and it hasfor its object to produce such a drill at one heat without cutting orturning the metal and in a manner to compact and solidify the steel inthe drill. The process also enables the drills to be produced cheaperthan by the usual methods and of the best quality.

In carrying out the invention the first step is to pass the heatedbillet through suitable rolls which draw the blank, form the twoopposite'longitudinal flutes therein, and form the taper shank andtenon. The next step is to drop-forge the rolled blank. This has theeffect to consolidate the metal and give the final size and finish tothe blank. The next step is to remove the fin from the blank which isproduced in the drop-forging, and this is done in suitable dies. Thenext step is the twisting of the blank by means of rapidly-reciprocatingdies, which further compact the metal, and the final step is the rollingof the drill to straighten it.

The process is effected at one heat, as before stated, and the productis a complete twistdrill, requiring only a little grinding and polishingto put the required finish thereon.

It will be noted that by this method of making a drill no metal is cutaway in forming the flutes and that the metal is compressed andcompacted at each step in the process except that of trimming off thefin formed in the forging. Furthermore, it will be noted that thesequence of the steps is conformable with the gradual fall intemperature of the blank during the process. For example, it isnecessary that the blank shall be quite hot when it is rolled. It mustnot be so hot during the twisting operation, and it should be at amoderate temperature when passed through the straightening-rolls.

By milling out the flutes or grooves in a blank for a twist-drill thegrain is cut across and the cutting edge is impaired, as well as thefying of the metal which is so necessary to the strength and to theproduction of a good gutting edge. This forging is effected in closeies.

The twisting is effected by means of hammering-dies in a machine of aknown kind, which keeps the metal compacted during the operation. Thedrill being forged and twisted while hot has not the tendency to warp intempering that is observable in a drill where the grooves are milled.

V The grinding of the drill has for its object the truing up andsharpening of the spiral cutting edges.

The process described avoids the necessity of annealing, which isrequired when the flutes or grooves are out, and this is very important,as the annealing and consequent hardening of the drill is quiteexpensive and the result is never satisfactory, as the steel losescarbon in annealing and the hardening process is only superficial.

In order to illustrate and set forth more clearly the process describedabove, reference may be had to the accompanying drawings, showingmechanical devices which may be employed in the series of operations.

In the drawings, Figure 1 shows the pair of rolls 1 for rolling theheated billet a to form in it the flutes and shank. This figure is on arelatively small scale. Fig. 2 is a cross-section of the dies 2 fordrop-forging the blank (0' to compact the metal and size the blank; andFig. 3 is a face or plan view of the-lower die, showing the blank inplace therein. Fig. 4 is a cross-section of the apertured die-plates 3and plunger i for removing the fin from the blank a, and Fig. 5 is aplan or face view of said plates. Figs. 6, 7, and 8 illustrate thedevice for twisting and hammering the blank a, Fig. 6 being afragmentary side elevation showing the series of raprdly-remprocatmgdies.

twisting-dies 5, Fig. 7 a cross-section at m in Fig. 6, and Fig. 8 anend View of one of said Such a twisting-machine is illustrated fully inmy United States Patent No. 719,988, dated February 10, 1903. Figs. 9and 10 illustrate the rolls 6 for straightening the drill a after it hasbeen twisted. Fig. 9 is a side elevation. It has not been deemednecessary to illustrate this straightening device in full, as a machinesuited for this purpose is fully illustrated in my United States PatentNo. 720,215, dated February 10, 1903.

Having thus described my invention, I claim The herein-described method0t forming a twist-drill, which consists in first rollinga heated steelbillet to draw the metal and form ROBERT L. BARCLAY.

Witnesses:

PETER A. Ross, H. A. CONN TT.

